L19_regulation of the Immune response

Question 1

What is tolerance?

Answer 1

The lack of response to a specific antigen.

Question 2

Is tolerance innate or acquired?

Answer 2

acquired

Question 3

What are the 2 major mechanisms of tolerance? What are the other 3

Answer 3

1 Deletion of reactive cells.
2 Inactivation of reactive cell: ANERGY
3 Functional Deletion
4 Generation of Suppressor or Regulatory Tcells (Treg)
5 Blocking of presentation or Activation

Question 4

Is anergy reversible?

Answer 4

No

Question 5

What is the major difference in the way T-reg cells interact with APC compared to other T-cells

Answer 5

It interacts with B7 via CTLA-4 instead of CD28 and then they send suppression signals to the T-cell

Question 6

How are T-Cells turned off after an immune response?

Answer 6

They start up-regulating CTLA-4 after a certain period of time and down-regulate CD28. CTLA-4 binds B7 with higher affinity and sends a suppressing signal to the cell.

Question 7

What are the mechanisms of tolerance in B cells?

Answer 7

1 Clonal Deletion
2 Clonal abortion/clonal Anergy
3 Functional Deletion

Question 8

Where does clonal deletion take place for B-Cells?

Is the level of deletion at this site higher or lower than what you see in the thymus with T-cells?

Answer 8

The Bone Marrow. Less deletion than in thymus with T-Cells

Question 9

If an immature B-cell in the bone marrow reacts with multivalent self antigen what happens? what it if reacts with solubilized self antigen?

Answer 9

Multivalent - apoptosis

Solubilized - Anergic B-cell in periphery (IgD predominately expressed)

Question 10

Describe which physical forms of an antigen favor an immune response and which favor tolerance

Answer 10

Immune- Large, aggregated, complex molecule

Tolerance- Soluble, aggregate-free, relatively smaller, less complex molecules not processed by APC

Question 11

Describe the routes of antigen administration that favor immune response and those that favor tolerance

Answer 11

Immune- SQ or IM

Tolerance- Oral or sometimes IV

Question 12

Describe the dose of an antigen that favors immune response versus tolerance

Answer 12

Immune- optimal dose

Tolerance- Very large or sometimes very small dose

Question 13

Describe the age of responding animal that favors an immune response versus tolerance

Answer 13

Immune- Older and immunologically mature

Tolerance- Newborn, immunologically immature

Question 14

Describe the differentiation state of cells that favor immune response versus tolerance

Answer 14

Immune- Fully differentiated cells; memory T and memory B

Tolerance- Relatively undifferentiated: B cells with only IgM, thymocytes

Question 15

What surface markers do Regulatory T-Cells Have?

Answer 15

FoxP3, CD25, CD4

Question 16

Why are immune responses to lipids and polysaccharides short lived?

Answer 16

Because you need protein immunogens to activate T-cells which cause B-cells to class switch to memory cells and give capability of secondary responses. T-Cells can only see protein.

Question 17

What is one way to try and limit responses to allergies?

Answer 17

Repeated small dose exposure

Question 18

What do adjuvants do?

Answer 18

They help keep antigen around for longer period of time, they also cause more of an inflammatory response. They can also help antigen be ingested and presented on cell surface. Creates more of a “DANGER” signal to the body.

Question 19

What type of immune response is necessary to fight off leprosy?

Answer 19

TH1

Question 20

What cytokines do Tregs secrete that actively turn off auto reactive T-cells?

Answer 20

IL-10 and TGF Beta

Question 21

What is the most important thing that must happen for something to be immunogenic?

Answer 21

It must be pagocytosed and presented such that a TCR can recognize it. Recognition by B-cells alone is not enough.

Question 22

How does a direct combs test work?

Answer 22

Washed fetal red blood cells coated with maternal antibody, add rabbit anti human and look for agglutination

Question 23

How does an indirect combs test work?

Answer 23

Maternal serum is added to Rh+ RBCs, wash, add rabbit anti human and look for agglutination

Question 24

What drug is given to mothers to prevent Rh antibodies from attacking th fetus?

Answer 24

Rhogam, works by hiding Rh antigen from mothers B-cells